It's the last scene of a film you've waited months to see. The villain makes a smug remark, stating that if his heart stops, a nuclear device in a distant shed will go off. The hero, of course, lowers his gun and pauses. Bomb triggers linked to vital signs often appear in fiction, making for an easy plot devices. But is modern technology finally making these fictional devices possible?

The character Raven in Neal Stephenson's cyberpunk classic Snow Crash has a nuclear bomb wired to his motorcycle that will explode should he die. Wizards in Dungeons & Dragons get the chance to cast one final spell prior to death. This is often called a "Dead Man's Switch," and fiction has made use of this time and time again.

A rudimentary, but deadly, version of this system exists in the real world. A trigger needing constantly pressure can be connected to a bomb, with this pressure preventing the bomb from detonating. These types of triggers are often used by suicide bombers, ensuring an explosion even if the bomber is shot and killed or otherwise disarmed.

These mechanisms do however have a lifesaving use. These switches are used everyday in municipal metro systems. The switches come in the form of handles or buttons that must be compressed by a driver in order for the passenger car to move forward. Should the transit worker suffer a disabling medical condition or die, the train car immediately stops as a safety measure. While this is an example of an all-or-nothing system — does a system exist that allows for a series of events to start should a fluctuation in vital signs occur?

Existing vital sign monitoring systems have evolved a great deal in the past decade, to the point where your physician can be immediately contacted by radio transmission or Bluetooth signal if your ticker goes awry. Corventis touts a "smart" band-aid called the PiiX that is placed of over the heart to detect anomalies and increases in heart rate. The data obtained is transmitted in real time to a physician or a designated point of care center. Patients can toggle the device to transmit data only corresponding to anomalous events or choose for the device to continually send full electrocardiograms.

Other options exist that allow for the monitoring of a wider array of vital signs, including Zephyr Technology's BioHarness. The BioHarness measures breathing rate and temperature in additional to cardiovascular data. Information is transferred via smart phones or radio signals to available apps and software. This type of harness is used to monitor the vital signs of firefighters, soldiers, and first responders.

The state of Pennsylvania requires prison guards to wear a unit that detects body motions across a 45° angle. Movement of this sort often denotes that a guard has been knocked down or is in an altercation with a prisoner, with the unit signalling an alarm to bring help.

While the systems necessary are intended to transfer health information to your physician, they don't rule out cases of transmission by deviant means if the recipient has criminal intentions in mind.

While a single-handed effort to detonate a bomb with a change in vital signs would take a large amount of wireless networking effort, using a willing third-party monitoring the vital signs to detonate the device should one's heart rate hit zero would be rather easy.

I can't debunk this one — triggering a bomb (or other device) with a decrease or change in vital signs is completely possible. Such a device would be nearly impossible to create two decades ago, but our wireless communication infrastructure and body monitoring technology has evolved to the point where this is a very real possibility. All that is needed is a couple of devious minds, destructive intent, and the use of existing commercial vital sign monitoring systems.

To move things to a little happier subject, you can use a modified form of a Dead Man's Switch to send your family, friends, and loved ones one last message should you expire prematurely. The website deadmansswitch.net allows you to store a series of e-mails (for free) that will be sent to designated individuals if you fail to click an e-mail link every 30-60 days. Of course, it might make for some interesting accidents if you migrate your e-mail account and forget to click the link.

Images courtesy of Corventis and Zephyr. Sources linked within the article.